Overbasing petroleum sulfonate additives for lubricating oils

ABSTRACT

A method of increasing the total base number of a metal petroleum sulfonate additive which involves recontacting the once carbon dioxide-contacted mixture with carbon dioxide under substantially the same conditions employed in the original carbon dioxide contacting. The carbonation is carried out on a discontinuous liquid phase of the additive which is in admixture with an inorganic base and with methanol.

United States Patent Gragson et al.

[ 51 Apr. 25, 1972 [54] OVERBASING PETROLEUM SULFONATE ADDITIVES FOR LUBRICATING OILS [72] Inventors: James T. Gragson, Bartlesville, Okla;

David W. Bosse, Joliet, Ill.

[73] Assignee: Phillips Petroleum Company 22 Filed: on. 7, 1969 [21] Appl.No.: 864,517

[52] U.S. Cl ..252/33, 252/18 [51] Int. Cl. ..Cl0m 1/40 [58] Field of Search ..252/l8, 33

[56] References Cited UNITED STATES PATENTS 3,384,585 5/1968 Gragson et a] "252/18 Primary Examiner-Daniel E. Wyman Assistant Examiner-l. Vaughn Attorney-Young and Quigg [5 71 ABSTRACT 8 Claims, No Drawings OVERBASING PETROLEUM SULFONATE ADDITIVES FOR LUBRICATING OILS This invention relates to increasing the base number of lubricating oil additives.

In one of its more specific aspects, this invention relates to a method of substantially increasing the base number of metal petroleum sulfonates. v

The use of metal petroleum sulfonates and overbased petroleum sulfonates as additives in combustion engine lubricating oils is well known. The effectiveness of such additives is enhanced by what may be considered to be their alkaline reserve, this being a measure of the extent to which they will act to neutralize the acidic products of the comhustion process.

One method of increasing the alkaline reserve of a metal petroleum sulfonate involves mixing it with a basic metal oxide or hydroxide and contacting it with carbon dioxide. As disclosed in US. Pat. No. 3,384,585, patented May 21, 1968, to Gragson et al., which patent is incorporated herein by reference, such a process comprises forming a mixture of the metal petroleum sulfonate, a hydroxide or oxide of a base metal and a diluent, adding methanol to the mixture, contacting the mixture as a discontinuous liquid phase with carbon dioxide under a pressure of from about to about 100 psig as a continuous gas phase, stripping the methanol from the gastreated mixture, filtering, stripping OK the solvent, and recovering the overbased metal petroleum sulfonate so produced.

By the use of such a process, base numbers, representative of alkaline reserve, of about 100, are easily achieved. However, it is desirable to produce sulfonates having even greater alkaline reserves and the method of this invention is directed to that end.

The method of the present invention is an improvement to the process of the aforementioned patent in that by use of the method of the present invention, considerably higher base numbers can be obtained. Accordingly, the method of this invention is an improvement in that process in which there is produced an overbased metal petroleum sulfonate by forming a mixture comprising metal petroleum sulfonate, a hydroxide or oxide of a base metal, a diluent, and methanol, contacting the mixture as a discontinuous liquid phase with carbon dioxide in a continuous gas phase and under a pressure of from about 10 to about 100 psig, and recovering from the mixture and overbased metal petroleum sulfonate, the improvement comprising recontacting the mixture of metal petroleum sulfonate, base, methanol, and diluent with carbon dioxide under substantially those conditions employed in the initial contacting step to further overbase the metal petroleum sulfonate.

In one embodiment of this invention, the overbased sulfonate is contacted with carbon dioxide in a plurality of contacting steps.

in one preferred embodiment of this invention, the carbonated mixture is stripped of its methanol and of the water produced in the first carbon dioxide contacting step and is again blended with fresh methanol before recontacting with carbon dioxide. After the final carbonation, when the desired level of overbasing has been reached, the mixture is stripped of methanol and water, filtered, and stripped of diluent to recover the overbased product.

In one embodiment of this invention, an additional quantity of a hydroxide or oxide of a base metal, such as calcium hydroxide, is added to the once-carbonated metal petroleum sulfonate mixture prior to its recontact with carbon dioxide.

The conditions employed in the subsequent contacting steps can be identical to those employed in the initial contacting steps; or the conditions employed in the subsequent contacting steps can be any conditions which would have been effective in promoting a first carbonation. It is also possible to recycle some portion of a subsequent contacted reaction product back to one of the previous contacting steps, or to pass only a portion of the previously contacted mixture through the subsequent contacting steps, reuniting the portions thereafter to control the total base number of the final product.

It is to be understood that the invention is also applicable to that method in which the originally formed overbased metal petroleum sulfonate is recovered from the reaction product and is introduced into a mixture none of the other components of which were present in the first contact step.

Accordingly, it is an object of this invention to produce sulfonates having high alkaline reserve.

It is also an object of this invention to produce overbased petroleum sulfonate additives whose concentration in the lubricating oils can be significantly decreased.

EXAMPLE I In this and the following examples of the operation of the method of this invention, the individual sulfonates employed were prepared by sulfonating a lubricating oil cut in the conventional manner, neutralizing the sulfonated product with calcium hydroxide, stabilizing it with a heat treatment, resulting in an intermediate product comprising calcium petroleum sulfonate, oil, naphtha, excess calcium hydroxide and quantities of inorganic salts formed during the neutralization step. This mixture is designated hereinafter as dryer tower bottoms and corresponds substantially to that material similarly designated in the aforementioned patent.

Slurries were produced by adding to individual amounts of dryer tower bottoms additional quantities of calcium hydroxide. The theoretically possible base number of each such slurry produced was determined in terms of equivalent milligrams of potassium hydroxide per gram of slurry, this being a function of the weight percent lime in the slurry, as follows: Theoretical base number in which K is assigned a value of 8, this being the base number of the untreated calcium petroleum sulfonate, it being assumed that this value remains unchanged during the subsequent carbonation step. Thus the theoretical base number is the base number which would be obtained if all of the lime were converted to a useful form, not removable by filtration but retained in the final recovered product.

In each instance, the carbon dioxide contact was conducted while maintaining the temperature of the slurry between about to about 120 F Water-free methanol was added before carbonation to give a methanol concentration of about 3.5 weight percent based upon the entire feed. The resulting mixture was introduced into the contacting zone in the form of small droplets and brought into contact with an atmosphere of carbon dioxide. The contacting zone was a vertical tower at the top of which were located a feed inlet and a C0 inlet. A liquid level was maintained in the bottom of the tower to provide a residence time of the treated feed of about 12 minutes. The tower was maintained at the given pressure by the regulated admission of CO Each of the several slurries, having different lime contents, were treated by this method. In each instance, the carbon dioxide-contacted efiluent had separated from it the methanol and the water and its total base number determined on a sample of from 0.2 to 0.3 gram. This sample was dissolved in ml of titrating solvent, the titrating solvent being a mixture of toluene and isopropyl alcohol containing 0.5 percent water, the sample being then titrated potentiometrically with 0.1 N aqueous hydrochloric acid to a pH of 4. The base number of the sample was expressed in milligrams of KOH/g of sample equivalent to the milligrams of HCl used in the titration.

"The once carbon dioxide-contacted, or carbonated products so produced had various total base numbers after one pass through the carbonation zone. Each of the once-carbonated products was stripped of methanol and water at about 250 F and remixed with a quantity of fresh methanol equal to that removed. The mixture was reintroduced into contact with TABLE I Garbonation zone a Passes Sulfo- Temperthrough Actual nateln ,Theoature, F. ,Prescarboprod- Sa'mplc feed, wt. retleal, sure, nation uet, Number .(percentfi TBN 1 in Out I p.s.i.g. zone TBN 17 7 675 96 110 25 1 177 17 7 676 87 112 35 2 282 16 640 '82 96 20 1 163 16 540 85 96 20 -2 M3 16 540 77 )4 l 3 301 16 540 85 92 20 4 336 10 540 93 111 25 1 205 10 540 85 115 25 3 352 10 3 600 87 101 15 5 402 608 84 101 35 1 182 4.; 1O 8 87 103 35 2 292 10 B 670 84 96 35 3 392 1 Percentage based upon sulfonate and naphtha only, lime and methanol excluded.

2 The theoretical base number is that base number which would have been'had by the final product had all the lime present been converted.

3 Estimated values, some additional lime having been added prior t the)? pass hr seu uet l .7 .7

The above data indicate the operability of the method of this invention. Theyfurther indicate that successive contacts according to the process of this invention act to greatly in- EXAMPLE ll A mixture, comparable to those employed in the runs of Table l, and comprising naphtha,- calcium petroleum sulfonate, methanol and lime, was agitated while in contact with 'a carbon dioxide atmosphere at 10 psig. Actual total base numbers were determined on the sample of the reaction mixture after various contact times with the following results:

TABLE n Contact time, Actual total Theoretical total minutes base number base number 'Thesedata indicate that merely providing additional contact time between the sulfonate mixture and a carbon dioxide atmosphere does not produce the results of the method of this invention. Instead, providing additional contact time, in itself, results ina decrease of actual total base number. whereas the method of this invention, which also provides increasedcontact time, produces the wholly unexpected result of increasing the actual total base number.

EXAMPLE lll :Relatedly, the unexpected results heretofore indicated cannot be attributable to the partial pressure effect of the carbon up dioxide as shown by the following data- These data are the results of the two runsmade under substantially identical con ditions except that in one the carbon dioxide pressure was 50 psig and in the other run the carbon dioxide pressure was psig.

lime concentration and a 3.8 weight percent methanol concentration, based upon the total feed mixture. Thisrfeed stream was reacted with carbon dioxide at an average inletoutlet temperature of aboutl00 F using the procedure and apparatus of Example I. Results were as follows:

TABLE III Theo- Product CO, retical total Run pressure, base base no. u psig [number l 50 i '603 I55 2 100' 603 90 These data indicate that the partial pressure of the carbon dioxide is not determinative of the total base number which is attained. Hence, the results of the practice of the methodof this invention are unexpected in consideration of the partial pressure effect of thecarbon dioxide in the above runs.

I EXAMPLE 1v Similarly, the above results cannot be attributable to varia- ,tions in concentration of lime as indicated by the following data which show that simply adding more lime to the overbasing system will not produce the results of the method of this invention. I v

Two runs were carried out under essentially identical conditions except in respect to the lime content. in each, naphtha solutions containing aboutj20 weight percent calcium petroleum sulfonate were mixed with lime and methanol, as in the runs presented in Table l. The solutions were carbonated at 35 psig in a carbonation tower, the inlet temperature to which was about 80 F and the outlet temperatures from which were about 1 10 F. After-one pass through the carbonator, the base number of the recovered products was determined. The results for each run as related to the theoretical base number, that is, the amount oflime employed, were as follows:

TABLE IV Theo- Actual' Effiretical product ciency, Run base total base percent no. no. no.

These data indicate that increasing the lime content of the carbonation mixture by a factor of about 5, as represented by the theoretical base number, resulted in only a nominal increase in the total base number. Hence, these data show that the improvement attainable by the method of this invention is not at? tributable to variation in lime content of the reaction mixture.

EXAMPLE v It can be similarly indicated that the results of the method of this invention are not attributable merely to the increased contact time afforded by the successive contacts between the oil and carbon dioxide.

The following table presents runs made by contacting an overbasing mixture containing naphtha, calcium petroleum sulfonate, methanol and lime with carbon dioxide at atmospheric pressure in a countercurrent contact zone. The naphtha solution contained about 25 weight percent calcium petroleum sulfonate, about 3 weight percent lime and about 3 weight percent methanol. Contact was made at about 85 F with the following being the results in terms of product total base number in relation to carbonation time.

During the carbonation, samples were taken at various intervals and the total base number of the product was determined. The results were as follows:

These data indicate that even in the presence of a substantial quantity of lime, the product reaches a maximum base number, and thereafter diminishes in base number, rather than reaching the high base number attainable by the method of this invention.

In summary, the control runs of Examples ll through V offer ample evidence that results in the art of overbasing calcium petroleum sulfonates are quite unpredictable. It was indeed surprising to obtain the high overbasing effectiveness in the invention runs of Example I.

It will be evident that various modifications can be made to the method of this invention as described herein. However, such are considered as being within the scope of the invention.

What is claimed is:

l. A process for producing overbased metal petroleum sulfonates which comprises:

a. forming a mixture comprising metal petroleum sulfonate,

a hydroxide or oxide of a base metal and a diluent;

b. adding methanol to said mixture;

c. contacting the mixture containing methanol as a discontinuous liquid phase with carbon dioxide in a first contacting step at a pressure of from about 10 to psig to produce an overbased metal petroleum sulfonate having a first theoretical base number;

d. separating said overbased metal petroleum sulfonate from said first contacting step and introducing the separated overbased metal petroleum sulfonate as a discontinuous liquid phase into contact with carbon dioxide under a pressure of from about 10 to about 100 psig in a second contacting step to produce an overbased metal petroleum sulfonate having a second theoretical base number greater than said first theoretical base number; and,

e. recovering said overbased metal petroleum sulfonate havin said second theoretical base number. 2. e method of claim 1 in which said overbased metal petroleum sulfonate having said first theoretical base number is introduced into step (d) in the absence of recovery from said mixture formed in step (b).

3. The method of claim 1 in which said overbased metal petroleum sulfonate having said first theoretical base number is recovered from said mixture, formed into a mixture comprising a hydroxide or oxide of a base metal, a diluent and methanol and introduced into said second contacting step.

4. The method of claim 1 in which said second contacting step is conducted under conditions substantially identical to the conditions of said first contacting step.

5. The method of claim 3 in which said overbased metal petroleum sulfonate having said first theoretical base number is recovered by stripping methanol and water from said mixture, filtering the stripped mixture and stripping the filtered mixture of diluent.

6. The method of claim 5 in which a hydroxide or oxide of a base metal is added to said overbased metal petroleum sulfonate having said first theoretical base number prior to introduction of said overbased metal petroleum sulfonate into said second contacting step.

7. The method of claim 1 in which a portion of the overbased metal petroleum sulfonate from said first contacting step is introduced into said second contacting step.

8. The method of claim 7 in which a portion of the overbased metal petroleum sulfonate from said first contacting step is recovered and formed into a mixture with the overbased metal petroleum sulfonate recovered from said second contacting step. 

2. The method of claim 1 in which said overbased metal petroleum sulfonate having said first theoretical base number is introduced into step (d) in the absence of recovery from said mixture formed in step (b).
 3. The method of claim 1 in which said overbased metal petroleum sulfonate having said first theoretical base number is recovered from said mixture, formed into a mixture comprising a hydroxide or oxide of a base metal, a diluent and methanol and introduced into said second contacting step.
 4. The method of claim 1 in which said second contacting step is conducted under conditions substantially identical to the conditions of said first contacting step.
 5. The method of claim 3 in which said overbased metal petroleum sulfonate having said first theoretical base number is recovered by stripping methanol and water from said mixture, filtering the stripped mixture and stripping the filtered mixture of diluent.
 6. The method of claim 5 in which a hydroxide or oxide of a base metal is added to said overbased metal petroleum sulfonate having said first theoretical base number prior to introduction of said overbased metal petroleum sulfonate into said second contacting step.
 7. The method of claim 1 in which a portion of the overbased metal petroleum sulfonate from said first contacting step is introduced into said second contacting step.
 8. The method of claim 7 in which a portion of the overbased metal petroleum sulfonate from said first contacting step is recovered and formed into a mixture with the overbased metal petroleum sulfonate recovered from said second contacting step. 